BEILIU, China -- For the past three decades, Qin Chenghao has lived the life of an ordinary farmer. He has tended to the trees covering the mountains that rise from the musty soil of southern China, harvesting the star-shaped fruit on their branches. Year after year, the same few traders arrive to buy his crop to sell as seasoning and traditional medicine.

This year, however, Qin's world changed. The star anise dangling from his trees emerged as a source for the key ingredient in Tamiflu, a pharmaceutical known to lessen the severity of avian flu. The output from his 1,300-acre Darong Mountain Star Anise Plantation in Guangxi province is now more than a simple means of spicing up stewed pork -- it is a crucial weapon in a global campaign against a pandemic that health experts say could kill tens of millions of people.

Qin's once-sleepy existence has given way to the life of an entrepreneur caught in a gold rush. The price of his crop has nearly tripled in the past four months, reaching about 80 cents per pound. Stocks have disappeared earlier in the season than anyone can remember, as Chinese pharmaceutical companies snap up what fruits they can to extract the shikimic acid contained within -- the substance that is the basis of Tamiflu.

"All of a sudden, our industry has become so important," Qin said, as he reached his chopsticks toward a plate of stir-fried wild greens before halting to answer a call on his cell phone. "Before, it was pretty quiet. Now, I answer my phone all day long. People call from all over the country. It's never been like this before."

With its semi-tropical climate and crowded cities and villages chockablock with pork and poultry farms, southern China is believed to be the source of the H5N1 avian influenza, which has been blamed for the deaths of at least 64 people in Asia since 2003. Now the very same area may hold the antidote as well. It literally grows on trees.

Dried star anise -- or bajiao , as it is called in Mandarin Chinese -- is a spice found in many Chinese kitchens, imparting a licorice-like taste to stewed meats. For as long as anyone can remember, Chinese doctors have prescribed bajiao to treat colic in babies, as well as headaches, abdominal pain and intestinal distress in adults.

More recently, farmers in northeastern China have mixed bajiao into animal feed because it keeps livestock warm through near-arctic winter months. Although most star anise is consumed domestically, a small export market also exists. The French, for example, are increasingly using star anise as flavoring for Pernod and other anisette liqueurs. And in the United States, star anise is found in five-spice powders available in grocery stores.

When Tamiflu was invented nearly a decade ago by researchers at Gilead Sciences Inc. in California, they used a different substance, quinic acid from the tropical cinchona tree. But when Roche Holding AG, the Swiss pharmaceutical giant, bought a license to make the drug, it substituted a form of star anise found in southwestern China.

This year, with bird flu hopscotching from Southeast Asia to Turkey to Britain, Roche has embarked on an expansion campaign aimed at increasing the production of Tamiflu tenfold over 2003 levels by the end of next year. Guangxi province -- home to 90 percent of China's star anise, which is itself the source of 90 percent of the global supply -- has become the heart of a crucial industry.

Health authorities do not recommend using star anise to try to ward off the flu. While production of Tamiflu starts with the acid contained in star anise, it involves multiple chemical steps, some using dangerous explosives, and the resulting drug does not remotely resemble the original material. Moreover, the U.S. Food and Drug Administration warned in 2003 that some star anise teas sold in health-food stores were making people dangerously ill. These were thought to be made from Japanese star anise, which contains a dangerous compound not present in the Chinese spice. The FDA warned that "Japanese star anise in its dried or processed form cannot be distinguished from Chinese star anise through visual examination."

In years past, little bajiao was purchased by pharmaceutical companies. Now, say traders, half the stocks are being bought by drugmakers, some of whom process star anise into shikimic acid for sale to Roche. Given that a freshly sprouted star anise tree takes six years to produce fruit, supply is likely to remain tight for some time.

Some 250 miles west of Hong Kong, this area lies far from the pharmaceutical laboratories where scientists contemplate preempting a pandemic. Peasants pedal bicycles past limestone hills, carrying ducks to market. Carts pulled by tractors haul coal to industrial furnaces. Farmers stand in the knee-deep muck of rice paddies under the shade of conical hats, hacking away with machetes at golden stems ready for harvest.

Qin, the general manager of the star anise plantation, has for years hired local villagers to pluck ripe fruit from his trees in the spring and fall. They dry the fruit on the ground under a pounding sun, then sell it to merchants from all over the country -- the first link in a complex distribution chain.

No one here seems to know what happens to the fruit after it is taken away, nor do most people grasp why more traders than ever are appearing. Some are vaguely aware of the connection to bird flu: Qin says he read about Tamiflu and star anise in a local newspaper. Most say they have heard nothing to explain the bonanza.

But they like the math involved. This year, Qin figures to earn $12,500 -- roughly double last year's income. He has invested his winnings into a local power plant venture, seeking to capitalize on another Chinese boom, the surging demand for energy.

Still, many villagers complain that they have not shared in the spoils because most sold their harvest before the price spike. If Chinese farmers have learned anything from their history, it is that famine and chaos can arrive with little warning. Conditioned against speculation, most farmers here sell what they have as soon as they have it.

"The middlemen make all the money," groused Lu Jimo, 81, as he laid out for sale a few small, plastic bags filled with the dried, burnt-amber fruit.

Usually, stocks of star anise last until Chinese New Year, in late January or early February. This year, most of the harvest was sold and shipped out in early November. Traders have grown desperate.

"They offer a high price and push us to find some," said Lan Zizhong, 26, a local middleman. "I get calls every day -- 'We'll take however much you can get' -- and I have to tell them I can't find any."

Much of the stock lands in a crowded market in the nearby city of Yulin, where traders come from as far away as northern China. Plastic sacks of dried star anise sit piled to the rafters in a warren of brick warehouses. But on a recent afternoon, little was for sale, amplifying the tight supply.

"We're holding on to what we have left to wait for a higher price," said Chen Chao, one merchant. "Every day, the price climbs."

As he spoke, a crew of men piled sacks high atop a truck headed for Anhui province in central China. A wholesaler from Zhejiang, a coastal province south of Shanghai, trolled the narrow alleyway for stocks for sale. Another crew pulled sacks from a warehouse to ready a shipment for Xian, a city full of pharmaceutical companies.

In a written statement, Roche said it relies on Chinese star anise for about two-thirds of its needed shikimic acid. The company said it is expanding efforts to increase production of the compound through a fermentation process that does not require star anise.

That might eventually cool the market here, and perhaps restore some tranquility. But obscurity might be gone forever.

"Now, all the foreigners know about us," Qin said.

Staff writer Justin Gillis and special correspondent Eva Woo contributed to this report.